These giant submarines were originally of the A2 type, but the design was
revised after construction started in order to enable them to carry a second
aircraft. The seaplanes were to be the Aichi M6A1, a bomber
able to carry a torpedo or an 800kg bomb. The range of these boats was
extraordinary, but underwater performance of these boats was badly compromised,
and these must have been exceptionally easy targets.

I-13 was sunk by destroyer escort USS Lawrence C. Taylor and aircraft from
escort carrier USS Anzio 550 miles east of Yokosuka on 16 July 1945. I-14
surrendered at sea at the end of the war, and was later scrapped.

Two additional ships were laid down, but not completed, and three more were
canceled.